Background : Measles virus is implicated in the etiology of Crohn's disease. This measles hypothesis is mainly supported by immunohistochemical findings that the measles-related antigen is present in the intestine of Crohn's disease. Recently we captured the measles-related antigen from the intestine of Crohn's disease using a molecular cloning technique and produced that monoclonal antibody, named 4F12, against it.Aim : The aim of this study was to disclose whether the measles-related antigen was uniquely present in Crohn's disease. Subjects and Methods : Colonic mucosa from 20 Crohn's disease, 20 ulcerative colitis, 11 non-IBD colitis, and 9 controls were immunohistochemically stained with the anti-measles monoclonal antibody 4F12. The numbers of positive cells, the ratio of positive cells to nucleated cells, and staining intensity of positive cells were compared. Furthermore, distribution of the measles antigen in other human organs were examined.Results : Both the number of positive cells and the ratio of positive cells to nucleated cells were significantly increased in Crohn's disease, ulcerative colitis, non-IBD colitis compared with controls (p<0.05) but were similar among three groups : Crohn's disease, ulcerative colitis, and non-IBD colitis. The staining intensity of positive cells was similar among the three groups. Small numbers of positive cells were observed in the esophagus, stomach, duodenum jejunum, and lung.Conclusion : Our results showed that the presence of the measles-related antigen in the colonic mucosa was not an unique phenomenon to Crohn's disease. These results together with the observation that such measles-related antigen was derived from host protein do not support the hypothesis that measles virus causes Crohn's disease.